8N , low oil pressure??

[gremlinx]

It's time for new rings, she's getting a lot of blow by. When it warms up, the oil pressure is barely 9 psi or so. Changed gauges, same reading. I hear 0 knock, so I suspect the oil pump is worn. What normally causes this with 8Ns?

 

[Egon]

Using it.

 

[Soundguy]

It's time for new rings, she's getting a lot of blow by. When it warms up, the oil pressure is barely 9 psi or so. Changed gauges, same reading. I hear 0 knock, so I suspect the oil pump is worn. What normally causes this with 8Ns?

as bearing tolerances and clearances in the block open up, you loose oil pressure. same with the pump.

best best is to rebuild the pump and line bore, put in new bearing shells and have crank turned, and have the cam hole in the block machined for inserts.

mind you that's alot of money.

If I was just doing a poor mans rebuild, I'd re0ring, ream the cyl ridges, slap in new shells same as the old size and then renew or stretch the oil relif plunger spring. If I was using a light grade oil, I'd go up one grade.. or go to a thicker multi grade.

9 psi is sure not bragging pressure.. but there are lots of em running on single digit oil pressure.

after new shells and thicker oil and the stretched spring I bet you get at least mid double digits which is fine for probably another decade of light to medium use..

soundguy

 

[Jerry/MT]

It's time for new rings, she's getting a lot of blow by. When it warms up, the oil pressure is barely 9 psi or so. Changed gauges, same reading. I hear 0 knock, so I suspect the oil pump is worn. What normally causes this with 8Ns?

These egines have realtively large journals for the loads that they carry and so can run without much damage at low oil pressures, but still low oil pressures are telling you that something isn't right.

If you have a lot of blowby, the engine is pretty warn and most likely the main bearings and oil pump clearances have opened up, too. The relief valve maybe stuck open and that can contribute to the problem. If you are going to rebuild it, replace the pump as part of the process, or at least check the clearances on the gears before you relace it. Clean the relief valve and check the spring height or replace the spring. I believe the relief valve is externally adjustable on the 8N so you might adjust that and see if it increases the oil pressure. Go up a weight in the oil. That will buy you some time to save your shekels for a rebuild.

 

[Soundguy]

externally adjustable in that you can remove the large plug by the water pump and pull the plunger and spring out and stretch the sprin to increase pressure on the plunger. rarely is it a miracules improvement.. but I have seen broke springs, or ones too short.. and in those cases, it made quite a difference.

heck.. between one grade thicker oil, assuming he's not already running 50w, new bearing shells, and at least a precursory check of the oil relief, he'll likely get into double digits.. that and a set of rings and a rented ridge reamer and a hand lap on the valves will probably be less than 100$ fro the head and pan gasket, shells, and valve compound.. oil and all. seen lots of poor mans rebuilds like that.. if it's not a 12hr a day plowing tractor, but rather a low to medium use machine.. that can buy alot of uptime...

soundguy

 

[trac]

On a rebuilt motor, I use the high volumn oil pump ( 9/16" gears). The relief valve spring can be shimmed to add oil pressure. Might try that first to increase oil pressure but, may increase blow by. Good Luck- trac

 

[ToadHill]

I switched to 20w50 oil in mine and raised the pressure by almost 15lbs when hot.

 

[Soundguy]

On a rebuilt motor, I use the high volumn oil pump ( 9/16" gears). The relief valve spring can be shimmed to add oil pressure. Might try that first to increase oil pressure but, may increase blow by. Good Luck- trac

I don't see how increasing the oil pressurewill increase combustion blow by on the rings significantly..

soundguy